The formation of insoluble metal sulfides in the environment may reduce the mobility and bioavailability of heavy metal contaminants and potentially eliminate the need for ex situ remediation of certain hazardous waste sites. To assist in assessing remediation strategies for the Bypass 601 Superfund site, groundwater aquifer samples were analyzed using synchrotron X-ray absorption spectroscopy (XAS) to determine whether lead and zinc sulfides were dominant mineral phases. Moist aquifer solids contained between 150 and 1800 mg of Pb/kg and between 100 and 250 mg of Zn/kg. Lead sulfide was not dominant in any of the samples analyzed, including one sample collected from a well in a flood plain that contained 70% of zinc bonded to sulfur, probably as ZnS. This portion of the aquifer had apparently been under reducing conditions. In all other samples, firstshell bonding of Pb and Zn was predominantly to oxygen. Data indicated that PbO, PbCO 3 , PbSO 4 , and ZnO were not dominant metal species. The XAS analyses showed that with one exception, metal sulfides were not prevalent.

A sensor based on rotational signatures in the submillimeter (SMM) region is described. This sensor uses frequency synthesis techniques in the region around 10 GHz, with nonlinear diode frequency multiplication to 210-270 GHz. This provides not only a nearly ideal instrument function, but also frequency control and agility that significantly enhance the performance of the spectrometer as a sensor. The SMM frequencies provide significantly stronger absorptions and broader spectroscopic coverage than lower-frequency microwave systems. Among the characteristics of the sensor are absolute specificity, low atmospheric clutter, good sensitivity, and near-term paths to systems that are both compact and very inexpensive.

We report the identification of several previously unidentified or misidentified lines toward OMC-1 as com-P?nents ~f. the J = 5--+ 4 a-type ba~d of _ 13 CH30H, deduced by combining accurate laboratory spectroscopy with sensitive broad-band astronomical hne searches. An L TE fit to the data yields a rotational temperature of T.ot"' 120 K and a 13 CH30H column density of -1.3 x 10 15 em -2 , averaged over a 30" beam. A 12 Cj 1 3C ratio of "'30 is derived. The assignment of the feature at 236063 MHz to the blended K = + 2 E transitions of 13 CH 3 0H, rather than to CO+, removes a major discrepancy between observation and the predictions of ion-molecule chemical models of dense interstellar clouds.

A technique for enhancement of positive molecular ion concentrations in a glow discharge is presented. The technique consists of modifying an anomalous glow discharge by the addition of a longitudinal magnetic field of up to 300 G. Enhancements in the ion signal strength, as measured by millimeter and submillimeter wave spectroscopy, are approximately two orders of magnitude. Evidence is presented that the magnetic field increases the length of the ion rich negative glow by restricting inside a small diameter tube the ionizing electrons accelerated by the large cathode drop of an anomalous glow discharge.

Over 250 rotational transitions of the internal rotor methyl formate (HCOOCH 3) in its ground (V 1 = 0) degenerate (E) torsional substate have been measured in the millimeter-wave spectral region. These data and a number of Estate lines identified by several other workers have been analyzed using an extension of the classical principal-axis method in the high barrier limit. The resulting rotational constants allow accurate prediction of the v 1 = 0 E substate methyl formate spectrum below 300 GHz between states with angular momentum J.:::; 30 and rotational energy Erot .:::; 350 em-1. The calculated transition frequencies for the E state, when combined with the results of our previous analysis of the ground symmetric, nondegenerate (A) state, account for over 200 of the emission lines observed toward Orion in a recent survey of the 215-265 GHz band.